Caleb Keeter of the Josh Abbott Band, which was part of the weekend lineup in Las Vegas, said he had changed his mind on the need for gun control after the shooting.CreditAmy Harris/Invision, via Associated Press

Country music artists and other performers expressed words of sympathy as well as frustration over gun violence on Monday as they mourned the mass shooting at a Las Vegas concert. One guitarist who played there said that the killings had changed his views on gun laws.

Some of these comments were politically striking, given that country music — which is widely popular across the nation — has a vocal fan base among gun owners. In 2010, the National Rifle Association started NRA Country to show “a softer side” of its organization. Its artist partners include some of the genre’s biggest stars, including Trace Adkins, Florida Georgia Line, Tyler Farr and Thomas Rhett.

The performer whose views had shifted — Caleb Keeter of the Josh Abbott Band, which was part of the weekend lineup in Las Vegas — said on Twitter on Monday that he had been “a proponent of the Second Amendment my entire life.”

He added, “Until the events of last night. I cannot express how wrong I was.”

Mr. Keeter, a guitarist, said that members of the band legally had firearms on the bus, but refrained from using them for fear the police would mistakenly think they were part of the attack.

“We need gun control RIGHT. NOW.” Mr. Keeter wrote. “My biggest regret is that I stubbornly didn’t realize it until my brothers on the road and myself were threatened by it.”

Mr. Keeter said he had written a living will and goodbye messages to his parents and partner on Sunday for fear that he would not survive the night. Members of his crew received shrapnel wounds, he said.

Country music is among the most popular genres in American music, particularly in live performances and on the radio. In 2016, country was the most-listened to radio format for the eighth consecutive year, topping news/talk radio and Top 40 with 13.6 percent of all listening, according to Nielsen. Large outdoor festivals like Stagecoach, Taste of Country and CMA Music Fest draw millions of fans every year.

Politically, the genre has long been associated with red states, especially in the South, and a conservative bent, even casting out some of its left-leaning, outspoken stars, like the Dixie Chicks, who faced a widespread industry boycott after criticizing President George W. Bush in 2003. While pop stars like Lady Gaga and Beyoncé closely aligned themselves with Hillary Clinton in last year’s election, country artists like Lee Brice and Chris Janson performed in support of Donald J. Trump at the Republican National Convention.

The Las Vegas attack, which killed at least 59 people, happened Sunday on the final night of the Route 91 Harvest Festival, a three-day country music event. Online video showed the singer Jason Aldean, who was listed as the festival’s final act, performing as the shooting began.

Mr. Aldean said early Monday that the attack was “beyond horrific.” He expressed further anguish on Tuesday, saying he was scared, angry and heartbroken.

“Something has changed in this country and in this world lately that is scary to see,” he said in a statement posted on Twitter. “This world is becoming the kind of place I am afraid to raise my children in.”

Mr. Aldean also called for unity. “Time to come together and stop the hate,” he said.

Jake Owen, a country singer who had performed earlier in the night, said on CNN on Monday that he was onstage with Mr. Aldean when the attack unfolded.

“It’s like shooting fish in a barrel from where he was,” Mr. Owen said, referring to the gunman, who the police said carried out the attack from a hotel room at the Mandalay Bay Resort and Casino. “I feel so bad for these people. We’re so lucky that none of us were in the line of fire.”

Mr. Owen added that the shooting continued for some time.

“This is not an exaggeration: This shooting was going on for at least 10 minutes,” he said. “It was nonstop.”

“I was running for my life like everyone else,” Mr. Owen added in a statement later on Monday.

“I wanted to post a photo of what this festival was supposed to be about and not give this horrible person the recognition he so desperately wanted,” Mr. Combs wrote. “I am incredibly saddened by tonight’s events and while I’m thankful that me and all of my band and crew are alive and unharmed, I can’t help but hurt for all the people who weren’t as fortunate and the pain their loved ones must feel.”

In a Twitter post, Kane Brown, a country singer who had performed hours before the attack, according to the schedule, offered prayers for Las Vegas. In another, he issued a four-word reaction: “This world is sick.”

John Rich, who performed in the festival as part of the duo Big & Rich, said on MSNBC on Tuesday that while he and his performing partner, William Kenneth Alphin, also known as “Big Kenny,” had left the venue by the time of the shooting, news of it reverberated up and down the Las Vegas strip as it unfolded.

“That devil up in the window could have had me, Kenny and everybody else up in his crosshairs,” he said.

Mr. Rich said it was hard to hear of fans who were injured or killed in the attack.

“It’s like watching your family out there going through this,” he said. “It’s unbelievable and it makes you want to bawl your eyes out, to be honest with you.”

Other country music stars weighed in as well. Shania Twain said she was “heartbroken.” Keith Urban said he was “stilled and speechless.”

“The laws the N.R.A. would pass are a threat to you, your fans, and to the concerts and festivals we enjoy,” she wrote in a New York Times Op-Ed. “The stakes are too high to not disavow collusion with the N.R.A.”

The pop singer Ariana Grande, whose concert in Manchester, England, was struck in May by a suicide bomber who killed 22 people and wounded hundreds more, wrote on Twitter, “My heart is breaking for Las Vegas,” and called for more gun control measures.

Britney Spears, whose show is running at Planet Hollywood in Las Vegas, said on Twitter that she was “completely heartbroken” by the attack. Jennifer Lopez and Celine Dion, who are also performing in the city, echoed that sentiment.

Mary Suh contributed reporting.

A version of this article appears in print on , on Page A17 of the New York edition with the headline: In Genre Linked to Gun Rights, Country Music Stars Recoil at Concert Slaughter. Order Reprints | Today’s Paper | Subscribe